Cancer is a disease that begins in the cells of a patient. The typical treatments for cancer include surgery, radiation, and/or chemotherapy. Because cancer varies from person to person, no single treatment may be effective for all patients. Typical surgeries for treating cancer include cutting, ablating, or otherwise removing an entire body part or just a portion of a body part where the cancer is located. Surgery, however, is not a viable option for many patients because of the location and/or type of cancer. Surgical treatments may also result in complications with anesthesia or infection, and surgical treatments may have long, painful recovery periods. Chemotherapy involves chemically treating the cancer. Chemotherapy is not a desirable option for several types of cancers and it can also have many complications.
Radiation therapy has become a significant and highly successful process for treating prostate cancer, lung cancer, brain cancer and many other types of localized cancers. Radiation therapy procedures generally involve (a) assessing the patient to determine a radiation prescription, (b) developing a treatment plan to carry out the prescribed radiation (e.g., dose, beam shape, beam angle, pulse width, etc.), (c) simulating treatment according to the treatment plan, (d) setting up a treatment session by positioning the patient in a radiation vault such that the target is at a desired location relative to the radiation beam, (e) treating the patient in one or more radiation sessions (i.e., radiation fractions) to irradiate the cancer, and (f) verifying or otherwise managing the treatment process to assess and modify the radiation sessions. Many radiation therapy procedures require several radiation fractions over a period of approximately 5-45 days. As such, many aspects of these procedures are repeated over this period and each procedure generates a significant amount of data.
To further improve the treatment of localized cancers with radiation therapy, it is generally desirable to increase the radiation dose because higher doses are more effective at destroying most cancers. Increasing the radiation dose, however, also increases the potential for complications to healthy tissues. The efficacy of radiation therapy accordingly depends on both the total dose of radiation delivered to the tumor and the total dose of radiation delivered to normal tissue adjacent to the tumor. To avoid damaging normal tissue adjacent to the tumor, the radiation should be prescribed to a tight treatment margin around the target such that only a small volume of healthy tissue is irradiated. For example, the treatment margin for prostate cancer should be selected to avoid irradiating rectal, bladder and bulbar urethral tissues. Similarly, the treatment margin for lung cancer should be selected to avoid irradiating healthy lung tissue. Therefore, it is not only desirable to increase the radiation dose delivered to the tumor, but it also desirable to avoid irradiating healthy tissue.
One difficulty of radiation therapy is that the target often moves within the patient either during or between radiation sessions. For example, the prostate gland moves within the patient during radiation treatment sessions because bowel and/or bladder conditions (e.g., full or empty) displace soft tissue structures within the body. Respiration can also displace tumors in the prostate gland. Tumors in the lungs also move during radiation sessions because of respiration and cardiac functions (e.g., heartbeats and vasculature constriction/dialation). To compensate for such movement, the treatment margins are generally larger than desired so that the tumor remains in the treatment volume. This is not a desirable solution because larger treatment margins generally result in irradiating larger volumes of normal tissue.
Conventional radiation therapy procedures address the problem of target movement with extensive treatment planning, simulation, setup, and verification procedures. Conventional treatment planning procedures are performed outside of the radiation vault well before the first radiation fraction. For example, conventional planning procedures typically involve obtaining CT images of the tumor and implanted gold fiducials to determine the size, shape and orientation of the tumor. These initial CT images are often not sufficient for carrying out radiation treatments because they do not address the internal motion of the tumor. As a result, patients may also undergo a simulation procedure using a different CT scanner that correlates the CT images in a time sequence to reconstruct the three dimensional volume and movement of the tumor. Using this data, the treatment margins can be set based on the observed trajectory of the tumor within the patient.
Conventional treatment planning procedures can be relatively expensive, require sophisticated equipment and technicians, and restrict the throughput of patients. For example, CT scanners are very expensive machines that require dedicated rooms because they use an ionizing energy for imaging the tumor and the gold fiducials. Additionally, the CT scanners for obtaining the initial images are typically different than the CT scanners that are used in the simulation procedures such that two separate dedicated areas with very expensive machines are required in these applications. Another concern of conventional planning processes is that the technicians subjectively interpolate the location of the tumor and the gold fiducials from the CT scans. This requires additional time and expense for skilled personnel, and it is also subject to human error. Still another concern of conventional planning procedures is that shuttling patients from one area to another and accurately managing the information restricts patient throughput. This may result in under utilization of the expensive equipment, facilities, and personnel. Therefore, conventional treatment planning procedures need to be improved.
Conventional setup procedures for aligning the tumor with the isocenter of the radiation beam are also an area of concern because they can be time-consuming and subject to error. Current setup procedures generally align (a) external reference markings on the patient and/or (b) internal gold fiducials in the patient with desired coordinates of the radiation delivery device. For example, the approximate location of the tumor is determined relative to alignment points on the exterior of the patient and/or gold fiducials in the patient. During setup, the external marks and/or gold fiducials are aligned with a reference frame of the radiation delivery device to position the treatment target at the beam isocenter of the radiation beam (also referenced herein as the machine isocenter).
Conventional setup procedures using external marks may be inadequate because the target may move relative to the external marks between the patient planning procedure and the treatment session and/or during the treatment session. As such, the target may be offset from the machine isocenter even when the external marks are at predetermined locations for positioning the target at the machine isocenter.
Conventional setup procedures using internal gold fiducials are also generally inadequate because this is a time-consuming process that may produce inaccurate results. In a typical setup procedure using gold fiducials, a technician positions the patient on a movable table in the radiation vault. The technician then leaves the room and operates an X-ray machine to acquire stereotactic X-rays of the target area. From these X-rays, an offset amount for moving the patient is determined. The technician then moves the table by the offset amount and acquires a second set of stereotactic X-rays to confirm that the position of the tumor is at the machine isocenter. This process may need to be repeated if the first sequence did not achieve the required placement. This process is time-consuming and may be unpleasant for the patient because the technician must vacate the radiation vault while the X-rays are acquired. This procedure may also be inaccurate because the patient may inadvertently move after taking the stereotactic X-rays such that the tumor is not at the location in the images. The potential inaccuracy of this process may be exacerbated because a person typically determines the offset by subjectively interpolating the CT images. Therefore, conventional setup procedures using gold fiducials tie up expensive linear accelerators in the radiation vault for extensive periods of time just to position patients for treatment, and conventional setup procedures may be inaccurate.
Another aspect of current radiation therapy techniques is to verify the performance of the radiation fraction and assess the status of the tumor for managing subsequent treatment fractions. Conventional verification systems record the status of the hardware of the radiation delivery device during a radiation session. For example, conventional verification systems record the beam intensity, beam position, and collimator configuration at time intervals during a radiation fraction. The hardware information from the radiation delivery device is then used to estimate the radiation dosage delivered to discrete regions of the tumor. Such conventional verification procedures, however, are subject to errors because the tumor is assumed to be at the machine isocenter throughout the radiation fraction. Moreover, the tumor is generally assumed to have the same size, shape and trajectory as determined in the planning procedure. The actual dosage delivered to the tumor may be significantly different because the tumor typically moves during the radiation fraction, or the tumor may have changed shape or trajectory after several radiation fractions because of the effects of the radiation. In conventional radiation therapy systems, the changes in shape or trajectory of the tumor can be determined using additional CT scans, but this requires additional time and use of expensive CT scanners and personnel. CT scans also expose the patient to more radiation. Therefore, conventional verification procedures can also be improved.
Another challenge of providing radiation therapy is that the information from the planning, simulation, setup, treatment, and verification procedures is typically generated from different equipment in various formats. Each stage of the process typically uses a stand-alone system that has unique formats/protocols that do not communicate with systems used at other stages of the process. This is inefficient because managing the data from the different procedures in a coherent, integrated manner may be difficult. For example, information from the CT scans, treatment plans, and the radiation sessions may be generated from equipment that uses different formats and/or protocols that are not compatible with each other. The information may accordingly need to be managed using some manual input or control. As such, expensive equipment and highly trained technicians are often under utilized because information is not readily available.